Apple's iPhone 5S and 5C have been on the market just seven weeks, but talk has already begun of what the Cupertino, Calif., company may have lined up for 2014's fall schedule.

On Sunday, the Bloomberg news service reported that Apple is designing and developing a pair of larger-sized iPhones that rely on curved screens similar to the one used in the Galaxy Round that Samsung debuted in its home country of South Korea last month.

Bloomberg, citing an anonymous source, said that the new iPhones, one with a screen size of 4.7 inches, another of 5.5 inches, would likely ship in the third quarter of 2014. Apple launched its annual iPhone refresh in that quarter the last three years.

Phablets have sold especially well in China, India, Hong Kong and South Korea. Researcher IDC, for example, noted in late August that sales of smartphones with screen sizes between 5 inches and just under 7 inches overtook those of notebook PCs and tablets combined in Asia during the quarter ending June 30.

But the form factor is much less popular in the U.S.

Apple's iPhone 5S and 5C -- as well as 2012's iPhone 5 -- sport a 4-in. display, measured diagonally. A 5.5-in. iPhone would be nearly as large as the "plus-sized" Galaxy Note 3 that Samsung launched in September.

The curved displays would be another new move by Apple and another imitation of rivals like Samsung, which sells a huge range of handsets powered by Google's Android mobile operating system.

Bloomberg did not specify what technology Apple would use for the curved screens, but the most likely would be a flexible OLED (organic light-emitting diode) display on a plastic substrate, which Samsung and LG both used in their smartphones.

Samsung's Galaxy Note 3 curves the screen downward from the left and right edges when the phone is held in portrait orientation; LG's G Flex curves the screen inward from the top and bottom. Apple's iPhone would presumably mimic the Galaxy.

While some industry analysts have called curved screens a marketing gimmick, some see such devices as design standouts, an important consideration for smartphones.

"If done right, a curved display could help a product stand out ... add a little more flair to the design," said Sameer Singh, an independent analyst who publishes the Tech-Thoughts website, in an email Monday.

Others argued that there were practical reasons why concave displays were smart.

A curved screen cuts down on ambient light reflections in several ways, said Raymond Soneira, president of DisplayMate Technologies and a long-time display expert. In turn, that has an impact on one of the pain points of smartphones: Battery life.

"[A curved screen] improves screen readability, image contrast, color accuracy, and overall picture quality, but can also increase the running time on battery because the screen brightness and display power can be lowered due to the reduced interference from ambient light reflections," Soneira wrote in an analysis of the Galaxy Round's screen published on his company's website.

Soneira was bullish on flexible screens, contending that they would have "a profound effect ... starting in the very near future" on display-based devices like smartphones and tablets.

Singh was skeptical, and instead speculated that while smartphone applications would be a niche at best, companies like Apple, Samsung and others were dabbling with flexible displays for other reasons.

"I think a lot of these companies may be seeding curved displays, in terms of manufacturing and 'field tests' through products like the Galaxy Round, for use on future wearable products, such as smartwatches," Singh said. Rumors have tracked an Apple smartwatch, dubbed "iWatch" by wags, for years, with some Wall Street analysts, disappointed that their predictions didn't come true in 2013, now forecasting an introduction next year.

U.S. mobile carriers have priced the Galaxy Note 3 between $250 and $300 with a two-year contract, or 26% to 51% more than the lowest-priced iPhone 5S. That led Singh to bet that, like Samsung, Apple would charge more for any larger smartphone.

"Given their business model, Apple's already gone as far downmarket as they can possibly go," Singh pointed out. "So a larger iPhone would either have to replace their flagship 5S or create a tier above that, starting at $749 [unsubsidized]."

Apple sells its 32GB iPhone 5S at that price without a subsidy, or $299 with a two-year contract.

Singh put his money on the latter. "I think certain sections of their core audience may prefer the 4-in. form factor," he said. "This also fits with their propensity to continually look upmarket, a strategy that carries its own risks."